Even though the automotive industry has over the years, if for no other reason than seeking competitive advantages, continually exerted efforts to increase the fuel economy of automotive engines, the gains realized thereby have been deemed by governmental bodies as being insufficient and such governmental bodies continue to impose increasingly stringent regulations relative to engine fuel economy as well as the maximum permissible amounts of carbon monoxide, hydrocarbons and oxides of nitrogen which may be emitted by the engine exhaust gases into the atmosphere.
In an attempt to meet such stringent regulations, the prior art has heretofore proposed the employment of a carburetor structure provided with electromagnetic duty-cycle valving means whereby the carburetor structure still functioned as an aspirating device but where the rate of fuel flow being aspirated is controllably modified by the duty-cycle valving means in response to feedback signals indicative of engine operation and other attendant conditions. Such carbureting structures, in the main, have not been found to be capable of satisfying the said continually increasing stringent regulations.
The prior art has also proposed the use of fuel metering injection means wherein a plurality of nozzle assemblies, situated as at the intake valves of respective cylinders of a piston engine, would receive fuel, under superatmospheric pressure, from a common fuel metering source and inject such fuel directly into the respective cylinders of the engine with such injection being done in timed relationship to engine operation. Such fuel injection systems, besides being costly, have not proven to be generally successful in that the system is required to provide metered fuel flow over a very wide range of metered fuel flows. Generally, those prior art injection systems which are very accurate at one end of the required range of metered fuel flows, are relatively inaccurate at the opposite end of that same range of metered fuel flows. Also, those prior art injection systems which are made to be accurate in the mid-portion of the required range of metered fuel flows are usually relatively inaccurate at both ends of that same range. The use of feedback means for altering the metering characteristics of such prior art fuel injection systems has not solved the problem of inaccurate metering because the problem usually is intertwined within such factors as: effective aperture area of the injector nozzle; comparative movement required by the associated nozzle pintle or valving member; inertia of the nozzle valving member; and nozzle "cracking" pressure (that being the pressure at which the nozzle opens). As should be apparent, the smaller the rate of metered fuel flow desired, the greater becomes the influence of such factors thereon.
The prior art has also heretofore proposed the employment of a throttle body with one or more electromagnetic duty-cycle type of fuel metering valving assemblies operatively carried thereby and spraying metered fuel, on a continual basis, into the air stream flowing through the throttle body and into the engine induction or intake manifold. Even though such arrangements, generally, are effective for providing closely controlled metered rates of fuel flow, they are nevertheless limited in their ability to meet the said increasingly stringent regulations. This inability is at least in part due to the fact that in such systems the throttle body is employed in combination with an engine intake or induction manifold through which the air and sprayed-fuel mixture is supplied to the respective engine cylinders. Because of design limitations, engine characteristics, cost factors and lack of repeatability in producing substantially identical intake manifolds, certain of the engine cylinders become starved for fuel when other engine cylinders are provided with their required stoichiometric fuel-air ratios. Consequently, the richness (in terms of fuel) of the entire fuel delivery system has to be increased to a fuel-air ratio which will provide the required stoichiometric fuel-air ratio to the otherwise starved engine cylinder or cylinders to obtain proper operation thereof. However, in so doing, the other engine cylinder or cylinders receive a fuel-air supply which is, in fact, overly rich (in terms of fuel) thereby resulting in reduced engine fuel economy and the increased production of engine exhaust emissions.
The prior art has also heretofore proposed the employment of a throttle body, which serves only to control the rate of air flow to an associated engine intake manifold, in combination with a plurality of electromagnetic duty-cycle type of fuel metering valving assemblies wherein respective ones of said plurality of duty-cycle valving assemblies are positioned in close proximity to respective ones of a plurality of engine cylinders as to thereby meter and discharge fuel into the induction system at respective points which are at least closely situated to the intake valves of the associated engine cylinder. In such an arrangement, it is often accepted practice to provide a common manifold of fuel, regulated at superatmospheric pressure, which feeds or supplies unmetered fuel to the respective duty-cycle valving assemblies where the metering function is performed. These systems are very costly in that a plurality of duty-cycle valving and metering assemblies are required and such valving assemblies, to obtain optimum performance, must be flow-matched to each other as sets for the engine. Further, in such arrangements, it is accepted as best practice to replace all duty-cycle valving assemblies upon failure of one or more in order to thereby again result in a matched set of injectors for the engine. Also, in such systems, if one of the injectors or duty-cycle valving means starts to malfunction, and if exhaust constituent sensor and feedback signal generating means are employed, the associated electronic control means will attempt to further increase or decrease (as the case may be) the richness of the fuel-air ratio of the remaining injector assemblies since the exhaust feedback signal cannot distinguish whether the change sensed in the exhaust constituents is due to one or more injector assemblies malfunctioning or whether the overall system needs a modification in the rate of metered fuel flow.
The invention as herein disclosed and described is primarily directed to the solution of the aforestated and other related and attendant problems of the prior art.